Which 1RM formula is most accurate?

Brzycki tends to be most accurate at 1-10 reps. Epley is the simplest and most commonly used. Both produce similar results within 5% of a true max for most lifters.

How accurate are 1RM estimates?

Estimates are most accurate at 1-5 reps. Past 10 reps the formulas overestimate because endurance becomes a bigger factor than pure strength.

Strength

One Rep Max Calculator

Estimate your 1RM from a working set. Three formulas — Epley, Brzycki, and Lombardi — averaged for a balanced number. Most accurate when reps are between 1 and 8.

The set you lifted

Estimated 1RM

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average across three formulas

Epley

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Brzycki

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Lombardi

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Training percentages

Reps	%1RM	Weight

The formulas

Epley: 1RM = weight × (1 + reps / 30) Brzycki: 1RM = weight × 36 / (37 − reps) Lombardi: 1RM = weight × reps^0.10

Which to trust?

Brzycki tends to be most accurate at low reps (1–8). Epley is the most popular and matches well in the 3–10 range. Lombardi is more conservative for high-rep sets. We average all three so you don't have to pick.

When to recalculate

Whenever you hit a clean rep PR — even one extra rep at the same weight nudges your estimate up by ~3%.

FAQ

What is a one rep max?

The maximum weight you can lift for a single rep with proper form. The reference for training intensity prescriptions.

Which formula is most accurate?

Brzycki at 1–8 reps. Epley is the most common. The averaged number here is more robust than picking just one.

How accurate are these estimates?

Within ~5% for sets of 1–8 reps. Past 10 reps the estimates inflate because muscular endurance dominates.

Should I actually test my 1RM?

Most lifters don't need to. A clean 3–5 rep set gives you all the data needed for programming. Test maxes are CNS-taxing and risky.

Want auto-calculated working weights?

FitBear logs every set, tracks your true 1RM trend, and prescribes weights based on it.

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